Hydraulic engine starting method



April 28, 1964 E. v. MANNING ETAL 3,130,540

HYDRAULIC ENGINE STARTING METHOD.

Filed Feb. l, 1962 2 Sheets-Sheet 1 ATTORNEYS April 28, 1964 E. v. MANNING ETAL HYDRAULIC ENGINE STARTING METHOD 2 Sheets-Sheet 2 Filed Feb. 1, 1962 my Nw NNW .WN -l INVENTORS {DWH/ED l/. ,MANN/N6 MD JAMES/Q. ,Dfw/e United States Patent 3,1341 540 HYDRAULIC ENGENE STAR'HNG METHQB Edward V. Manning and .lames R. Farr, Watertown, FLY.,

assignors to The New Yori: Air Brake Company, a corporation of New .Hersey Filed Feb. 1, 1962, Ser. No. 170,440 3 Claims. (Cl. dil- 17) This invention relates to hydraulic starting and pumping systems.

The use of hydraulic motors for starting internal combustion engines is known in the prior art. Such hydraulic motors are generally driven by pressure iluid supplied by motor-driven auxiliary pumps and the known systems have proven to be complex, heavy, space-consuming and expensive.

The copending applications of Edward V. Manning and lohn P. Mentink, Serial No. 92,052, iiled February 27, 1961, and of Melvin L. Kent and Mike Prewarslti, Serial No. 111,721, led May 22, 1961, disclose hydraulic starting stystems utilizing variable displacement motorpump units that, during the starting operation, are supplied with iluid from a source, such as a pressure accumulator, having a decaying pressure characteristic. The displacement control element of the motor-pump unit in these systems is maintained in maximum displacement-establishing position substantially throughout the starting cycle, i.e., until the engine has accelerated to approximately starter cut-out speed, and is then moved to a neutral or zero displacement-establishing position. When the engine accelerates to a speed at which it is capable of driving7 the unit as a pump under load, the displacement control element is shifted overcenter to reverse the direction of iow through the unit and cause it to discharge hydraulic iiuid under pressure. This fluid is used to recharge the accumulator and, if desired, to operate auxiliary power-operated devices. These systems have many advantages among which are the facts that it is completely self-contained and does not require separate starting and pumping units. Furthermore, since the starting method performed by both of these systems requires that the motor-pump unit be operated at maximum displacement throughout substantially the entire starting cycle, maximum torque is applied to the engine. However, this mode of operation requires a large capacity accumulator and in some cases does not give optimum performance.

The object of this invention is to provide a method of starting an engine using a variable displacement hydraulic unit and a source of pressure uid having a decaying pressure characteristic which reduces materially the capacity of that source. According to this invention, the hydraulic unit is operated at maximum displacement for only a portion of the starting cycle, for example, until the engine has accelerated to about 50% of stan-er cut-out speed, and thereafter the displacement is reduced progressively toward zero at a rate proportional to engine acceleration. it has been found that this mode or operation derives the required starting torque from a source having a capacity of only about 90% of the capacity of sources required by the methods of the above mentioned copending applications.

The preferred starting method of this invention is described herein in relation to the accompanying drawings in which:

FIG. 1 is a sectional view of the hydraulic unit of the starting system, the displacement control member being shown in its maximum stroke-establishing motoring position.

FIG. 2 is a schematic diagram of the hydraulic starting system, the displacement control element of the hydraulic unit being shown in its Zero stroke-establishing neutral position.

The hydraulic starting system illustrated in the drawings is basically the same as the one disclosed in the Kent and Prewarslii application mentioned above and includes a Variable displacement hydraulic motor-pump unit 3 of the overcenter type disclosed in detail in the copending application of Tadeusz Budzich and Edward V. Manning, Serial No. 789,996, filed January 29, 1959, and entitled OVercenter Hydraulic Starter Pump. The hydraulic unit comprises a housing 4 containing a drive shaft 5 to which is connected the rotary cylinder barrel 6. One end of rotary barrel 6 is in sliding engagement with the face of a stationary valve plate 7 which contains arcuate high and low pressure ports communicating, respectively, with the housing high and low pressure ports 8 and 9 illustrated in FIG. 2 through internal housing passages (not shown). The cylinder barrel 6 contains a circular series of through longitudinal cylinder bores 11 which register sequentially with the arcuate ports in valve plate 7 as the cylinder barrel rotates. Pistons 12, formed with spherical heads 13 that support shoes 14, are mounted in the cylinder bores for reciprocation by cam plate 15 and return plate 16.

The cam plate 15 is supported in housing 4 by yokes 15a and trunnions 17 (see FIG. 2) for angular movement about an axis extending in a direction normal to and intersecting the axis of drive shaft 5. The angular position of cam plate 15 determines the length of the strokes of pistons 12, and the cam plate is free to move between maximum stroke-establishing positions on opposite sides of a zero stroke-establishing neutral position. Shiftable spring assembly 18 is provided for biasing cam plate 15 in the clockwise direction about its pivot axis. This spring assembly comprises a iirst spring seat sleeve 19 connected at one end with the cam plate 15 by connecting rod 21, a second spring seat sleeve 22 arranged for sliding movement at one end within an axial bore in the other end of sleeve 19, and a coaxial preloaded coil compression spring 23 seated on the peripheral ilanges 19a and 22a of sleeves 19 and 22, respectively. When sleeve 22 is in its FIG. 1 position in engagement with the housing wall surface 4a, spring 23 biases sleeveV 19 to the left and thereby places cam plate 15 in its maximum stroke-establishing position on the pumping side of neutral (indicated by the broken lines in FIG. 2).

Motor means 24 are provided for shifting sleeve 22 to the left to increase the bias exerted by spring 23 during pumping operation. This motor 24 includes a cylinder 25 having an axial tubular extension 25a and a reciprocable piston 2d carrying a piston rod 27 that projects into tubular extension 25a. The second sleeve 22, which is mounted for sliding movement on this tubular extension 25a, is formed with an end Wall 22h against which the free end of piston rod 27 abuts. When pressure duid is introduced into working chamber 24a of motor 24 to displace piston 26 to the left into enengagement with the left-hand end Wall of cylinder 25, piston rod 27 shifts sleeve 22 to the left and thereby compresses spring 23. It is important to note that when sleeve 22 is in this left-hand position, it serves as a limit stop that prevents cam plate 15 from moving from its neutral position toward its FIG. l position.

Cam plate 15 is movable in the counterclockwise direction against the biasing force of spring assembly 18 by a hydraulic positioning motor 31 including a cylinder 32 secured to housing 4 and a reciprocable piston 33 that is connected with cam plate 15 by connecting rod 34. Piston 33 is moved to the left in its cylinder by the pressure fluid in working chamber 31a.

The drive shaft 5 extends through an opening in the housing and terminates in a splined coupling 36 to which the internal combustion engine 37 is connected via conventional mechanical coupling 38.

Referring now to FG. 2, an accumulator 40, which constitutes a pressure fluid source having a decaying pressure characteristic, is connected with the high pressure port 8 of the motor-pump unit 3 via conduit 41 containing a three-way selector valve 42 having a first position in which it interconnects conduit portions 41a and 41b and a second position in which it interconnects conduit portion 41b and the vehicle hydraulic system conduit 43. Housing low pressure port 9 is in continuous communication with sump 44 through conduit 45.

The state of energization of positioning motor 31 is controlled by a dual-pressure control valve 46. This control valve includes a housing having an inlet passage 47 connected with high pressure port S via conduit 4S, a motor passage 49 connected with positioning motor working chamber 31a via conduit 51, and an exhaust passage 52 connected with sump 44 via conduit 53. The control valve housing includes a longitudinal bore 54 in one end of which is mounted the reciprocable valve plunger 55 formed with lands 56, 5'7 and S separated by grooves 59 and 61, respectively, for controlling communication between the various valve housing passages 47, 49 and 52. Through longitudinal slots 62 are provided in the outer periphery of land 58.

Mounted for reciprocation in the other end of the valve housing bore 54 is a spring seat 63. Preloaded coil compression spring 64, reacting between seat 63 and plunger 55, urges the seat to the left to its FIG. 2 position in which it abuts housing Wall projection 65, and urges the plunger 55 in the opposite direction into engagement with the other bore end wall to effect venting of the working chamber 31a of positioning motor 31 via conduit 51, passage 49, groove 59, passage 52 and conduit 53. Spring chamber 66 is in continuous communication with sump conduit 53 via conduit 67.

When seat 63 is in its FIG. 2 position, spring 64 establishes a first reference pressure condition of operation of control valve 46 as will be described in greater detail below. When pressure fluid is introduced into working chamber 63a to shift seat 63 to the right to a second position in which it engages fixed stop 69, the preload in spring 64 is increased to establish a second reference pressure condition of operation of control valve 46.

Working chamber 24a of shifting motor 24 and Working chamber 63a are pressurized and vented simultaneously by auxiliary valve 71. This auxiliary valve includes a housing having an inlet port 72 connected with high pressure port 3 via conduit 73 and conduit portion 48a, a motor port 74 connected with working chamber 24a via conduits 75a and 75h and with working chamber 63a via conduits 75a and 75e, and a pair of exhaust ports 76 and 77 connected with sump 44 via conduits 78 and '79, respectively. The valve housing contains a longitudinal bore which receives the reciprocable valve plunger 81 carrying lands 82, 83, and 84 separated by grooves 85 and 86. Spring 37, mounted in the left-hand end of the longitudinal bore, biases plunger 81 to the right to an energizing position in which working chambers 24a and 63a communicate with high pressure port 3 via branch conduit portions 75b and 75e, respectively, common conduit portion 75a, port 74, groove 85, port 72, conduit 73 and conduit portion 48a. Plunger 81 carries an axial projection Sla on which is secured the armature 88 of stationary solenoid coil 89. When solenoid coil S9 is energized by closing switch 91, armature 88 is displaced to the left by magnetic attraction to move plunger 81 to the left to its venting position, shown in FIG. 2, in which working chambers 24a and 63a are connected with sump 44 via branch conduit portions 75b and 75e, respectively, common conduit portion 75a, port 74, groove 36, port '77, and conduit 79.

Motoring Operation Assuming that the hydraulic motor-pump unit 3 is at rest and that selector valve 42 is in its second position, the

fluid path from accumulator 40 to high pressure port 8 is closed and the initial pressure in port and control valve inlet chamber 47 are zero. Plunger 55 of control valve 46 is maintained in its FIG. 2 position by spring 64 so that working chamber 31a of positioning motor 31 is vented to sump via conduit 51, passage 49, groove 59, passage 52 and conduit 53. Assuming also that switch 91 is closed to energize solenoid 89, plunger S1 of the auxiliary valve 71 is maintained in its FIG. 2 venting position against the bias of spring 87 and working chambers 24a and 63a are connected with sump 44. Since working chamber 24a is vented, spring seat sleeve 22 engages the housing wall surfact 4a and spring 23 biases sleeve 19 to the left relatively to sleeve 22 to position cam plate 15 in its maximum stroke-establishing position on the pumping side of neutral, as shown by the broken lines in FiG. 2. Since working chamber 63a is vented, seat 63 is in its FIG. 2 position and spring 64 establishes the first reference pressure value against which the pressure in inlet passage 47 is compared.

For the purpose of the following discussion, it will be assumed that the lirst reference pressure established by spring 64 is 1400 p.s.i., that the accumulator 40 is charged to an initial pressure of 3000 p.s.i., and that pressures of 1400 and 1900 p.s.i., respectively, in working chamber 31a are required to hold cam plate 15 in the neutral position of FIG. 2 and the maximum motoring position of FIG. l against the bias of spring 23 when chamber 24a is vented.

When inlet valve 42 is opened, pressure fluid is transmitted to port S, through conduit 41 and to inlet passage 47 to control valve 46 via conduit 48. The liuid in passage 47 acts on the right-hand end surfaces of lands 57- and 53 and shifts plunger 55 to the left against the bias of springs 64. As the pressure rises to the reference value of 1400 p.s.i., plunUer 55 moves to a lap position in which land 57 interrupts communication between motor passage 49 and exhaust passage 52. A further rise in pressure in inlet passage 47 causes plunger 55 to move further to the left to interconnect inlet passage 47 with motor passage 49 through slots 62 and groove 61. Pressure uid is now transmitted to Working chamber 31a through conduit 51. The pressure in working chamber 31a rises rapidly to system pressure, and since at this time this pressure is greater than the 1900 p.s.i. required to hold cam plate 15 in the maximum stroke-establishing position on the motoring side of neutral (see FIG. l), the motor 31 immediately moves the cam plate 15 to that position. The cam plate 15 remains in this position as long as system pressure is above 1900 p.s.i.

The uid supplied to high pressure port 8 from the accumulator 40 is fed through internal housing passages (not shown) and through the ports of valve plate 7 to the longitudinal bores 11 of the rotary cylinder barrel 6 to shift pistons 12' to the left against cam plate 15. The pistons react with the inclined cam plate to apply maximum initial torque on drive shaft 5 with the result that internal combustion engine 37 is driven in the starting direction by the hydraulic unit 3 through the splined coupling 36 and the mechanical connection 38.

As the speed of rotation of the hydraulic motor 3 increases, it imposes an increasing demand on the accumulator 4t) and consequently the supply pressure decreases progressively. For the purpose of this discussion, it is.

15 in its maximum stroke-establishing motoring posi-- tion against the bias of spring 23. Consequently the hydraulic unit 3 continuously applies to the internal Vcombustion engine 37 the maximum possible torque ob-V tainable from the fluid pressure source. As the engine speed increases above 50% of starter cut-out speed, ac-v cumulator pressure, and consequently the pressure in working chamber 31a, decreases below 1900 p.s.i. and spring 23 commences to move cam plate 15 in a clockwise direction toward the zero stroke-establishing position. This movement of the cam plate progressively decreases the displacement of hydraulic units 3 and, since the rate of decay of accumulator pressure is proportional to engine acceleration, so too is the rate of change of displacement. In a typical case, the flow demand per unit of time imposed on the accumulator increases to a maximum at about 60% of starter cut-out speed and thereafter decreases progressively until cut-out speed is reached.

As accumulator pressure approaches 1400 p.s.i., the internal combustion engine approaches starter cut-out speed and plunger 55 of control valve 46 begins to move toward lap position. When system pressure reaches 1400 p.s.i., the engine will have achieved independent operation and will be driving hydraulic unit 3 as a pump, ca m plate will be in zero stroke-establishing position, and valve plunger 55 will be in lap position. Since there is no demand for hydraulic fluid at this time, system pressure will remain at 1400 p.s.i. and control valve 46 will maintain cam plate 15 in neutral position. However, should system pressure decrease as a result of leakage, spring 64 will shift valve plunger 55 to the right from the lap position to thereby vent working chamber 31a and permit spring 23 to move cam plate 15 away from neutral position a small distance in the direction of maximum stroke-establishing position on the pumping side of neutral. This action causes the pump to supply fluid to the system and when the pressure is restored to 1400 p.s.i. and the rate of discharge from the pump equals the rate of leakage, plunger 55 will be shifted back to the lap position. It should be realized that the cam plate position established by system leakage is very close to the neutral position and that for all practical purposes, the hydraulic unit is now imposing a minimum torque on the internal combustion engine. This is a desirable feature because it permits the engine to accelerate rapidly.

Pumping Operation After the internal combustion engine has accelerated to a speed at which it develops sullicient power to drive the hydraulic unit 3 under load, switch 91 is opened to initiate the high pressure pumping operation. Opening of switch 91 deenergizes the holding solenoid 89 and allows spring S7 to move valve plunger 31 to the right to connect working chambers 24a and 63a with high pressure port 8 via branch conduits 75b and 75C, respectively, common conduit 75a, port 74, groove 85, port 72, conduit 73 and conduit portion 48a. The pressure uid in Working chamber 24a moves piston 26, piston rod 27, and sleeve 22 to the left to increase the biasing force applied to cam plate 15 by spring 2.3. Sleeve 22 now constitutes a stationary cam stop preventing movement of the cam plate from its neutral position toward its maximum stroke-establishing position on the motoring side of neutral.

The pressure fluid in working chamber 63a moves spring seat 63 to the right into engagement with stop 69 with the result that the compression load in spring 64 is increased to establish a second reference pressure value (for example, 3000 p.s.i.). Plunger 55 now moves to its FIG. 2 position thereby venting chamber 31a and permitting spring 23 to move cam plate 15 to its maximum stroke-establishing position on the pumping side of neutral.

With cam plate 15 in its maximum stroke-establishing pumping position, the hydraulic unit 3 supplies fluid from high pressure port S to the accumulator 40 via conduit 41. As the accumulator pressure rises to 3000 p.s.i., which is the second reference pressure, plunger 55 is shifted to the left to its lap position. When the pressure exceeds 3000 p.s.i., plunger 55 is shifted further to the left to admit uid to chamber 31a via slots 62, groove 61, chamber 49 and conduit 51 and cause motor 31 to move cam plate 15 to its neutral position. Because of the presence of the cam stop (i.e., sleeve 22 in its left-hand position), movement of the cam plate in the counterclockwise direction beyond the neutral position is prevented. Since the cam plate is now in its neutral position, the hydraulic unit is in an idling, minimum-displacement condition. In the event that the pressure in conduit 48 drops below 3000 p.s.i. (as a result of internal leakage, for example), plunger 55 is shifted to the right by spring 64 to vent chamber 31a and allow spring 23 to move cam plate 15 in a clockwise direction, to effect an increase in displacement of the unit 3. When the pressure in conduit 4S is returned to 3000 p.s.i., plunger 55 is moved to the left to the lap position to trap the fluid in chamber 31a, whereby cam plate 15 is maintained in its leakage compensating position.

Selector valve 42 may now be shifted to its second position in which accumulator 40 is isolated and high pressure port 8 is connected with the vehicle hydraulic ssytem via conduits 41b and 43. As a result of system demand, the pressure in conduit 48 and passage 47 decreases below 3000 p.s.i. and plunger 55 is shifted to the right to vent Working chamber 31a. Cam plate 15 now pivots in the clockwise direction toward its maximum stroke-establishing pumping position under the action of spring 23. When the system demand is met by the pump, the pressure in conduit 48 rises to the second reference pressure value and plunger 55 is shifted to the left to its lap position to discontinue venting of chamber 31a. The position of the cam plate 15 now establishes a rate of discharge equal to the rate of demand for hydraulic fluid.

Should the system demand decrease and the pressure rise above 3000 p.s.i., plunger 55 is shifted further to the left to supply fluid to chamber 31a, and thus cause motor 31 to effect a progressive decrease in cam angle. When the cam reaches that position in which the rate of discharge from the hydraulic unit 3 matches the new demand and system pressure is restored to 3000 p.s.i., plunger 55 moves back to its lap position and again interrupts flow to working chamber 31a. Thus it is apparent that during pumping operation, the hydraulic unit operates as a pressure-compensated pump, the displacement of which is automatically varied by valve 46 to maintain substantially constant the selected maximum system pressure.

As stated previously, the drawings and description relate only to the preferred embodiment of the invention. Since changes can be made in this embodiment without departing from the inventive concept, the following claims should provide the sole measure of the scope of the invention.

What we claim is:

1. The method of accelerating an engine to starter cutout speed during a starting cycle using a Variable displacement hydraulic motor comprising the steps of (a) supplying uid to the motor at a pressure that decreases as the length of time the motor operates increases;

(b) operating the motor at maximum displacement from the beginning of the starting cycle until the engine has reached a certain speed substantially less than cut-out speed; and

(c) thereafter progressively reducing motor displacement toward zero as the engine accelerates to starter cut-out speed at a rate proportional to engine acceleration.

2. The method of accelerating an engine to starter cutout speed during a starting cycle using a variable displacement hydraulic motor comprising the steps of (a) supplying uid to the motor at a pressure that decreases as the length of time the motor operates increases;

(b) operating the motor at maximum displacement from the beginning of the starting cycle until the engine has reached a certain speed substantially less than cut-out speed; and

(c) thereafter progressively reducing motor displacement toward zero Vas the engine accelerates to starter cut-out speed at a rate that is a function of the rate of decrease of pressure of said supply uid.

3. The method of accelerating an engine to starter cutout speed during a starting cycle using a variable displacement hydraulic motor and a charged pressure accumulator as a source of motive uid comprising the steps of (a) transmitting fluid from the accumulator to the motor to drive the motor and thereby accelerate the engine;

(b) operating the motor at maximum displacement from the beginning of the starting cycle until the accumulator pressure has decreased to a certain Value;

and

References Cited in the le of this patent UNITED STATES PATENTS Volk Sept. 8, 1953 Hogeman Aug. 13, 1957 

1. THE METHOD OF ACCELERATING AN ENGINE TO STARTER CUTOUT SPEED DURING A STARTING CYCLE USING A VARIABLE DISPLACEMENT HYDRAULIC MOTOR COMPRISING THE STEPS OF (A) SUPPLYING FLUID TO THE MOTOR AT A PRESSURE THAT DECREASES AS THE LENGTH OF TIME THE MOTOR OPERATES INCREASES; (B) OPERATING THE MOTOR AT MAXIMUM DISPLACEMENT FROM THE BEGINNING OF THE STARTING CYCLE UNTIL THE ENGINE HAS REACHED A CERTAIN SPEED SUBSTANTIALLY LESS THAN CUT-OUT SPEED; AND (C) THEREAFTER PROGRESSIVELY REDUCING MOTOR DISPLACEMENT TOWARD ZERO AS THE ENGINE ACCELERATES TO STARTER CUT-OUT SPEED AT A RATE PROPORTIONAL TO ENGINE ACCELERATION. 